(1) Field of the Invention
The present invention relates to a single pole, double throw switch with a stable off position, and more particularly to a single pole, double throw self-canceling rotary switch with a freely rotating shaft that does not affect the status of the switch when rotating in one direction, and cancels the switch when rotating in the other direction.
(2) Description of Related Art
According to U.S. National Highway and Traffic Safety Division Standard No. 108, part S5.1.1.5, encoded at 49 CFR 571.108, the turn signal operating unit on most motor vehicles must be self-canceling by steering wheel rotation, and capable of cancellation by a manually operated control. Additionally, such devices are nearly universal in motor vehicles equipped with a steering wheel worldwide.
Many implementations of turn signal switches use a single pole, double throw self-canceling switch with a stable off position. In general, an electric switch is a device that includes two or more electrical contacts that are arranged such that they can be selectively moved into and out of contact with each other. Switches can include one or more poles, or electric contacts coupled to single circuit elements. Switches are frequently classified by the number of poles and the number of possible switch positions, or throws, per pole. FIG. 1 schematically illustrates a single pole, double throw switch, in which the pole COM is selectively connected to a first position L1 or a second position L2. Such switches may also include a stable off position, in which the pole COM is neither connected to L1 nor L2.
A typical turn signaling system of an automobile is illustrated in FIG. 2. The system includes a battery 10, an electrical controller 12, a turn signal flasher 14, a turn signal switch 16, a left turn signal 18, and a right turn signal 20. When the automobile is turned on, the electrical controller 12 provides electric power from the battery 10, through a fuse panel, to the turn signal flasher 14. The turn signal switch 16 includes a lever (not illustrated) controlled by the driver of the automobile that, when pushed in one direction, couples the turn signal flasher 14 to the left turn signal 18, and when pushed in the other direction, couples the turn signal flasher 14 to the right turn signal 20. The turn signal switch is usually self-cancelling, meaning that, for example, when the turn signal switch 16 is switched to connect the left turn signal 18, the turn signal switch 16 will return to the off position after a left turn is complete.